Quick-break circuit breaker



2 Sheets-Sheet l Filed Aug. 9 195i .Ill-1 fag INVENTOR.

Ulu-mm /meazo afm/Nas' @BY QUICK-BREAKv CIRCUITv BREAKER Filed Aug. 9.`1951 2 Sheets-Sheet 2 United States Patent 2,769,049 QUICK-BREAKCHKCUIT BREAKER William Harold Edmunds, Havertown, Pa., assignor toI-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation ofPennsylvania Application August 9, 1951, Serial No. 241,013 2 Claims.(Cl. 200-67) My present invention relatesl to circuit breakers and moreparticularly it relates to circuit breakers of the quick-make andquick-break type for lighting circuits, that is, circuit breakers whichclose or open their contacts in very small intervals of time, preventingtherefore an arc from being maintained betweencontacts for a .period oftime longer than desirable.

Asis well-known in the art, a circuit breaker has both automatic openingmeans and manual opening means. The automatic opening means, which canbe thermal or electro-magnetic, or a combination of thermal andelectromagnetic, open the circuit breaker contacts whenever a faultcurrent is present in the electrical circuit protected bythe circuitbreaker;

ince fault currents are usually large, it is desirable that the contactsof a circuit breaker open very quickly so that the arc produced betweenthe contacts during the. vopening;movement be maintained for theshortest possible time.

The manual. opening means instead open the circuit breaker whenever itisldesired to interrupt the electrical circuit protected by thecircuit.breaker vwhen only the usualfload current flows through this electricalcircuit. This meansthatthe contactsof the circuit breaker when manuallyoperated must interrupt theV usual load current, much smallerrthan afault-current. But even this smaller current can produce considerabledamage to the contact surfaces and the circuit breaker if the contactsmove open very slowly in that an' arc between contacts nwould bemaintained` for an undesirably long periodof time.

It is thus seenthat it is also necessary `tohave a quickbreak actionwhen the circuit breaker is opened-manually.

ln constructing circuit breakers for lighting use, it is essential thatthe circuit breaker be relatively compact Y and inexpensive. This hasbeen achieved. by mounting a movablecontact for direct operation pivotedto and movable by ahandle. l p

A cradle in a togglel mounting is latched so that -a spring secured at'one end to the cradle-and at the other end to the movable contact arm ison onerside of the movable contact arm biasing it open when the Contactis openjand' biasing it closed when the' contact this beingA achievedas'noted` above'by a toggle' operation.

Inforder to prevent the lcontacts-from sticking tol each otherat-*autom'atic opening of the circuit bre'aker and then welding, akicker is-'provided; vthis kicken-consisting is closed, 1

ofa kickingwmember operateduby a pin mounted on the 2; contacts areiirst pried apart by this fulcrum action before the overcenter spring isover center, that is, before the over center spring can come intooperation and snap, in a small interval of time, the contacts open. v Inother words, an arc will exist between contacts for the interval of timestarting when the movable contact assembly strikes the cradle and-endingwhen the spring is over center and, therefore, capable of assisting -theinitial opening operation. v v

My present-invention overcome this shortcoming by providing a cradle ofsuch shape and so positioned with respect to themovablecontact` assemblythat duringl the manual opening operation, the movable Contact assemblyVnever even-touches the cradle, thus avoiding the fulcrumactionpreviously described.

The main object of my present invention is, therefore, the Vprovision ofmeans whereby a circuit breaker has quick-break action not only duringautomatic opening of the contacts due to fault currents but also duringmanual opening of the circuit breaker contacts.

Furthermore, my invention can beeasily applied to presently manufacturedcircuit breakers Without having to change the assembly of said breakers.p

Accordingly, another object of my present invention is the provision ofmeans wherebypresently manufactured circuit breakers can be madequick-break also during manual opening with a minimum amount of laborand without changing the assembly of said circuit breakers.

in previous types of circuit breakers, theposition of the stationarycontact was such that butt-type contact engagement existed between,movable and stationary contact. This type* ofiontact engagement does notpermit the contacts to wipe .themselves clean during-the` closing andopening nio-veinent.Vv Thisshortcoming is overcome by my presentinvention by placing the ,stationarycontact'- yin suchl a location thatthe two contacts slide with respect to eachother and, therefore, wipethemselves clean during lthe closing andy opening movements.

Accordingly, another object of myv present invention is'thel provisionof means cuit breaker Vwipe themselves cleanduring the closing andopening movements'.

The foregoing and manyother objects of my inventionY will becomeapparent in the following description and drawings lin which:

Figure 1 is a sectional IView of a circuit breaker incorporating myinvention showing the circuit breaker vin the open position. i

Figure 2 i's a sectional view partly broke-n away of a circuit breakerincorporating my invention showing 'the circuit breaker in the closedposition.

Figure 3 is a schematic view of the movable mechanism of the circuitbreaker of my invention.

Figure 4 is a sectionalfvie'w fof thecircuit breaker shown in Figures land 2 inthe open position after an opening caused by fault currents. I

, Figure 5 is aside view of the circuit breaker shown in Figures l andA2.l Y f Referring now to Figures4 l" and 5v, the -honsing 10 is ashallow' boX, preferably a plastic insulatingv moulding, having a coverplateV 11 which ca'nbe secured to housing 10 by` any suitablev means,for example, bolts and nuts place'din the appropriatel aligned openings12 of the housing'll) and cover plate 1l. g f i The stationary contactassembly 15 Vconsists of al contact button 16 welded to one bent'end 17vof aconducting member V18.' Member 18- is slidably mountedi'n housing10; that is, it can Vbeslid in and'out of housing `1,0 when cover plate11 is removed. The other end 20 of conductingmember 18 has acenteropening 21 threaded inside to be engaged lby a terminal screw 22 whichserves to 'secure the wir'e`(not shown) to one terminal 20 of wherebythe contacts of a cir-l the circuit breaker. The other terminal of thecircuit breaker is similarly provided with a screw 26 engaging a Contactmember 28 and securing the other wire (not shown) to this secondterminal Z5.

Contact member 28 of rectangular cross-section is shaped like an angleand is secured to housing 10 by means of any appropriate means, forexample, a screw 30. One end of angle 28 as above described has theterminal screw 26, while to the other end is secured by means of a screw31 or other suitable means a thermally responsive member 35. The otherend 36 of thermally responsive member is connected by soldering or otherappropriate means to a flexible conductor or pigtail 40.

A leaf spring is riveted to the end of thermally responsive member 35nearer to screw 31. Leaf spring 45 extends beyond end 36 of thermallyresponsive member 35 carries an insulating button 47 riveted to leafspring 45 and capable of making contact with one side of thermallyresponsive member 35.

Pigtail 40 is connected on one side to end 36 of thermally responsivemember 35 and on the other to the movable contact member 50 to which itis soldered. Contact member 50 has the shape of a U or that of a tuningfork and has an extension 51 at the bottom of the U which carries brazedto it a contact 55 engageable in the circuit breaker closed positionwith stationary contact 16.

Each extension 56 of U-shaped member 50 engages a groove 'or notch 58 ofmoulded plastic handle 60. Handle 60 is provided with two coaxiallaterally extending trunnions 65, one of which engages an appropriateopening (not shown) in housing 10 and the other engages anotherappropriate opening (not shown) in cover plate 11, thus rendering thehandle 60 movable in opposite directions in opening 66 of housing 10.

An overload responsive member `70 approximately hook-shaped has anopening at one end 71. Opening 71 is aligned with anv opening (notshown) in boss 72 which is part of moulding 10. A pin 75 engages bothopenings 71 ofoverload responsive member 70 and the opening in boss 72of housing 10.

The other end 77 of overload responsive member 70 engages normally alatch 80 rigidly secured to leaf spring 45 by means of a rivet 81. Rivet81 also secures the armature of an overload responsive magnet 90 to leafspring 45 on the side Opposite that in which latch 80 is located.Overload responsive magnet consists of a rectangular piece of metal witha central recess 91 to receive thermally responsive member 35 to whichit is secured also by a rivet or any other suitable means.

Between opening 71 and end 77 of hook-shaped member 70 is anotheropening 95. An over center tension spring 10i? placed between legs 56 ofU-shaped member 50 engages on one side an opening 101 at the apex ofU-shaped member 50 and on the other side opening 95 of overloadresponsive member 70.

Between openings 71 and 95 is a third opening 105 which receives a resetrod 11i). Overload responsive member 70 has also rigidly secured to itrod 115 engageable with slot of a contact kicker member 125. Contactkicker member pivoted at one end by means of pin 126 engaging anappropriate recess 127 in moulding 1t) is provided in the center withthe angularly shaped slot 120 and at the other end with an extension 129whose function, as hereinafter described, is to assist the initialopening movement of the movable contact 50 during opening operationcaused by a faultcurrent.

ln other words, the kicker 125 kicks the movable contact 55 away fromstationary contact 16 after the over center spring 100 has been movedover center during automatic opening, thus preventing contacts 55 and 16from sticking to each other.

An arc chute 130 consisting of conducting U-shaped t l plates 131 isplaced in the path of operation of movable and forms a U at its farthestend 46. End 46` contact 55 to extinguish the arc developed during theopening operation of the circuit breaker.

Referring now to Figure 2 showing the circuit breaker of my invention inthe closed position, the over center spring 1G@ is on one side ofcontact member 50 and more precisely for this embodiment, the overcenter spring 100 is at the left of contact member 50, thus biasingcontact 55 against stationary contact 16.

When a fault current flows-in the circuit protected by the circuitbreaker andits magnitude is below a certain predetermined maximum, thethermally responsive member 35 will become suliciently heated andsulliciently bent in the direction of insulating button 47 to engagebutton 47` and pull leaf spring 45 in such a direction that extension 77of hook-shaped member 70 is freed from engagement with latch Stb so'that hook-shaped member 7@ will rotate around pivot pin 75.

Rotation of hook-shaped member 70 will bring the over center spring 10)to the other side of contact member 50 passing through a position ofunstable equilibrium on which the longitudinal axes of contact arm 5t)and of spring 109 are substantially parallel and extend through thegroove or notch 58, thus biasing contact member 50 away from stationarycontact 16 and providing a snap opening of contacts 55 and 16. Rotationof hook-shaped member 70 during an opening caused by overload produces amovement of Contact kicking member 125 around the pivot pin 126 throughmotion of rod 115 of member 70 in slot 120 of contact kicking member125. This movement occurs just after spring 100 has been moved overcenter. v

During its motion, contact kicking member 125 hits with its extension129 one leg of U-shaped contact member 50, thus prying the contacts 55and 16 open and providing an additional snap action during the openingmovement of contacts 16 and 55 producedby a fault current.

When the fault current is larger than a certain maximum, instead magnet90 due to the current flowing through thermally responsivemember 35 willbecome su'iciently magnetized to pull its armature 85 and, therefore,also leaf spring 45 toward thermally responsive member 35, thusdisengaging extension 77 of hook-shaped member 70 from latch 80. Themovements following this disengagement are the same as those describedabove in connection with the thermally responsive member 35.

When open by fault current, the circuit breaker parts will be positionedas shown in Figure 4. Handle 60 will be positioned in the neutralposition while spring 100 will bias contact member 56 toward hook-shapedmember 70, but contact member 56 and extension 77 will remain separatedby boss of moulding 10.

The closing operation consists of two steps from the position shown inFigure 4. First handle 60 is rotated to the full open or off position.During this movement,V the two extensions 140 carrying groovesSS engagereset rod 110 and move rod 110 and, therefore, also member 70 in thedirection opposite to that followed by member 70 during the openingoperation. When handle 60 is in the full open or off position, extension77 of member 70 will have engaged latch 80 `and the position `of thevarious parts of the circuit breaker will be that shown in Figure 1.

To close the circuit breaker, it is now only necessary to move handle 60to the closed or on position. During this motion of handle 60,extensions 56 of contact memberv 50 rotate in grooves 58 of plastichandle 60, thus moving contact member 50 rst against the bias of overcenter spring 100 which is now on the right side of contact 50 (seeFigure 1).

If this motion is continued, a position for contact member 50 will bereached in which contact member 50 will be. slightly to the left `ofover center spring 100.` At this time spring 100 will bias contactmember 50 toward stationary contact 16, thus providing a quick makeaction during the closing of contacts 55 and 16. p

If the fault still persists while the operator is closing the circuitbreaker and has his hand on the operating handle 60, the automaticopening mechanism made operable again by the above-described movement ofhandle 60'in the yf-ull open position will operate and will allowU-shaped member 70 to rotate around its pivot 75, thus causing, asabove-described, the separation of contact 55 ffrom contact 16.

When, on the other hand, the circuit breaker is to be opened manuallysince member 70 does not movel during manual opening of the Icircuitbreaker, no contact kicking I'action is provided in addition to the snapaction of spring 100. Y

More specifically, yas the operator moves the handle 6.0from-full closedto -full open position, in Figure 3 from left to right, extensions 56 ofU-shaped con-tact member 50 rotate in grooves 58 of handle 60, thusmoving, the contact member extensions '56 toward the left in theembodiment shown withA respect to spring 100. 'I'he openingzof contacts55 and 16 .occurs only when extensions 56 are actually at the left ofspring 100, that is, when spring 100 is over center to the right ofextensions 56 and, therefore, capable of imparting la snap `action tocontact member 5t).v v In Figure 3, my novel circuit breaker is shown atthe time when spring 100- is still to the left of extensions 56 ofcontact member 50 but extensions 56 arev moving toward the -left ofspring 100.

As is evident from Figure 3, as handle 60 is moved from closedto openposition, in the igure from left. to right, extensions 56 move towardspring 100 until they go beyond opening 100. At this point, spring 100becomes operative yand capable of producing a snap action opening ofcontacts 55 and 16.

Contrary to what happens in the older types of circuit breakers, whenthe circuit breaker mechanisms are in the position of Figure 4, contacts55 and 16 are not pried apart because neither boss 72 nor section ofmember 70 around pin 75 act now as a fulcrum during the initial leftwardmovement orf-both contact member extensions 56 and spring 100.

As above-mentioned, no initial opening of contacts 55 and 16 will occurwhen my invention is used with the result that contacts 55 and 16 willnot be damaged by a prolonged arc.

As previously mentioned in older types of circuit breakers butt typecontact engagements were obtained between movable and stationarycontacts. This type of contact is undesirable in that no contact slidingcan occur between the contact surfaces of contacts 55 and 16 with theresult that these contact surfaces never wipe each other clean.

This shortcoming is overcome in my invention by placing contact 16 atend 17 of member 18 away from moulding 10 as shown in Figure 4 so thatwhen contacts 50 and 16 either come in contact `or go out of contactthey always wipe their contact surfaces one against the other, producingthe necessary cleaning of the two contact surtaces.

In fact, when handle 6) is moved from the full closed to the full openposition, that is, from the position shown in Figure 2 to the positionshown in Figure 1, contact arm 50 slides initially in the longitudinaldirection with respect to its axis lor radial with respect to the centerof rotation of contact arm 50 if contact 16 makes a certain angle withsurface 19 of moulding 10 as shown more clearly in Figure 3.

This initial sliding movement of contact arm 50 permits wiping ofmovable contact 55 and stationary contact 16.

To summarize the above, since circuit breakers for lighting circuitsmust be very small and inexpensive, their movable contact arm 50 ispivoted to and movable by ing is latched by latch 80 so that a spring100 secured at one end of cradle opening and on the other end to opening101 of movable contact arm 50 is on one side of the movable contact `arm56 biasing it open when contacts 55 and 16 are not in contact andbiasing the contact arm 50 closed when the contacts 55 and 16 are incontact, this being achieved as above-describedbya toggle operati-on.

In order to move spring over center by movement of cradle 7), cradle 70had to be extended into the path ofv spring 100 and had to be pivotedaround pin 75 engaging opening 751 in boss 72- of housing 10 away fromhandle 60 or better away lfrom fulcrum 58 of handle 50 so that it actedin older embodiment as a fulcrum for spring 100 and movable contact arm50 and tended to preventquick break action during manual opening.

In the circuit breaker of my` invention, as previously described, quick`break action is present -not only when the circuit breaker isautomatically opened but also when the circuit breaker is manuallyopened. Th'isim'- provement is obtained by so shaping cradle 70 and boss72 of moulding-10 that a clearance is always present between spring 100on one side and cradle 70 and boss 72 on the other.

In `the foregoing I have'described my invention solely in connectionwith speoiic illustrative embodiments thereof. Since many variations andmodifications of my invention will now be obvious to those skilledin-the art, I prefer to be bound not by the speciiic-disclosures hereincontained but only by the appended claims.

Ilclaim:

l. In a circuit breaker for opening withl a snap action; a stationarycontact, a movable contact arm carrying ya movable contact, said armhaving a circuit closed position in which its movable contact engagessaid stationary contact and a circuit open position in which saidcontacts are disengaged, a pivotally mounted operating handle having amanually operable end on one side of the pivot mounting and having anotch on the opposite end and other side of the pivot mounting, saidmovable contact arm being pivotally mounted in said notch and extendinglongitudinally substantially in the longitudinal direction of saidhandle with said movable contact on the end opposite the pivotalmounting of said arm, a substantially U-shaped cradle having one endlate-hed and pivotally mounted lat its opposite end, a spring, one endof said spring being secured to said movable arm adjacent its contactcarrying end and the opposite end of said spring being secured to saidcradle at the apex of the U-shaped cradle, said movable arm and springextending between the legs of said -cradle and into the loop tormed bythe substantially U-shaped cradle, the apex of said U being adjacent tothe notch of said handle, said handle having a closed and an openposition and being manually operable to an intermediate position inwhich said contacts are engaged in unstable equilibrium, said movablecontact on said movable contact arm having y relative motion to andremaining in electrical engagement with said stationary contact as saidhandle is moved from closed position toward circuit open position, toef- Ifeet a wiping action between said stationary and movable contactuntil said notch and arm have been moved from said circuit closedposition to the position of unstable equilibrium; said conta-ct arm andspring being spaced from said boss when said contact arm and said springare in the position of unstable equilibrium and said contacts are inengagement in unstable equilibrium so that full` contact engagement ismaintained at the unstable equilibrium position and any slight furthermovement of said handle moves this notch to the other side of thetension spring for applying a snap action opening force to said movablecontacts.

2. In a circuit breaker for opening with a snap action; a plasticmoulded housing and a cover plate, .a stationary contact, a movablecontact arm carrying a movable contact, said arm having a circuit closedposition in which its movable contact engages said stationary contact, acircuit -open position in which said contacts are disengaged, apivotally mounted operating handle having a manually operable end on oneside of the pivot mounting and having a notch on the opposite end andother side yof the pivot mounting, said movable contact larm beingpivotally mounted in said notch and extending 1ongitudinallysubstantially in the longitudinal direction of said handle with saidmovable contact on the end opposite the pivotal mounting of said arm, asubstantially U-shaped cradle having one end latched, said plasticmoulded housing having a boss extending therefrom to receive a pivotpin, said U-shaped cradle pivotally mounted at its opposite end on saidpivot pin of said boss, a tension spring, one end of said `tension`spring being secured to said movable arm adjacent its contact carryingend and the opposite end of said tension spring being secured to saidcradle at the apex of the U-shaped cradle, said movable arm and springextending between the legs of said cradle and into the loop formed bythe substantially U-shaped cradle, Ithe apex of the said U beingadjacent the notch of said handle, said handle having a closed and anopen position and 'being manually operable to an intermediate positionin which said contacts are engaged in unstablev equilibrium, saidmovable contact -on said movable contact arm initially having relativemovement to and remaining in electrical engagement with said stationarycontact as said handle is moved from closed position toward circuit openposition, said stationary contact secured to said plastic mouldedhousing, the axis through the center of said stationary contact having:a first predetermined angle with respect to the axis through the centerof said movable contact when said contacts are in engagement in saidcircuit closed position and having a second predetermined angle withrespect to the axis through the center of said movableV contact ywhichis different `than said rst predetermined angl-e when said contacts arein engagement in said unstable equilibrium to eiect a wiping actionbetween said iixed `and movable contact until such notch and arm havebeen moved from said circuit closed position to the position of unstableequilibrium on which the longitudinal axis of said arm and tensionspring are substantially parallel and extend through the center of thenotch, said boss having a substantially circular conligurationg .acutaway portion on said substantially circular boss to preventengagement of said tension spring and said contact arm with said boss atlast mentioned parallel position; said tension spring and contact armspaced from said boss and pivot pin so that full contact engagementvcontinues at the unstable equilibrium position and any slight furthermovement of said handle moves it notch to the other side of the tensionspring for applying a snap action opening force to said movable contact.

References Cited in the le of this patent UNITED STATES PATENTS

